Stereophonic electronic piano

ABSTRACT

An electronic piano is provided with keyboard operated or controlled tone generators providing electric oscillations corresponding to piano tones. These oscillations are amplified by an amplifier, and are applied to two loudspeakers located at opposite ends of the keyboard. The loudspeaker at the left end of the keyboard is adapted to reproduce the piano bass tones at relatively high efficiency while the loudspeaker at the right end of the keyboard is adapted to reproduce the treble tones at relatively high efficiency, whereby the tones throughout the gamut of the piano are located primarily at the same locations relative to the keyboard as they would be on a mechanical or conventional string piano. A third speaker is provided on the panel below the keyboard to simulate sound emanating from a piano soundboard.

United States Patent Andersen [54] STEREOPHONIC ELECTRONIC PIANO [72] Inventor: Clifford W. Andersen, De Kalb, lll.

[73] Assignee: The Wurlitzer Company, Chicago, Ill.

[22] Filed: Mar. 12, 1969 [2]] Appl. No.: 806,610

[ 1 Feb. 15, 1972 OTHER PUBLICATIONS Leonard Feldman The Case For A Third C hannel", RADIO & TV NEWS, March 1959, pp 70, 7|, I04 & 105 George J. Healy Adding. A Center Speaker For Stereo, ELECTRONICS WORLD, Vol. 66, No. 2, Aug. 1961. pp 40, 41, & 88.

Primary Examiner-Lewis H. Myers [52] US. Cl ..84/ 1.01, 84/DlG. 1, 179/ l G, Assistant Examiner-Stanley J Witkowski 1 179/1 M Attorney01son, Trexler, Wolters & Bushnell [51] Int. Cl. G10h 1/00 [58] Field ofSearch ..84/l.01, 1.16,1.04, 1.17; [57] ABSTRACT l l 1 1 TD An electronic piano is provided with keyboard operated or controlled tone generators providing electric oscillations cor- [56] Reierences cued responding to piano tones. These oscillations are amplified by UNITED STATES PATENTS an amplifier, and are applied to two loudspeakers located at opposite ends of the keyboard. The loudspeaker at the left end 2,323,231 6/1943 Merrel ..84/D1G. 1 of the keyboard is adapted to reproduce the piano bass tones 3,056,327 10/1962 Schwartz et al... ....84/1.25 at relatively high efficiency while the loudspeaker at the right 3,272,906 9/1966 De Vries et al. ....84/1.25 end of the keyboard is adapted to reproduce the treble tones 3,497,604 2/ 1970 Welsh et al. .,..84/1 .01 v at relatively high efi'lciency, whereby the tones throughout the 2,513,109 6/1950 Roth ....84/1.l8 gamut of the piano are located primarily at the same locations 2,596,258 5/1952 Leslie ....84/1 .01 relative to the keyboard as they would be on a meehanieal or 3 2l 5 li ill N; /11" conventional string piano. A third speaker is provided on the .7 7/I966 wchl'mflnn panel below the keyboard to simulate sound emanating from a piano soundboard.

5 Claims, 4 Drawing Figures J 52 L? Z STEREOPIIONIC ELECTRONIC PIANO Electronic organs have reached a high state of perfection in the simulation of pipe organs or the like tones, and a great number of different makes have been sold with commercial success. However, this is not at all true with respect to electronic pianos. Although it is possible through the use of electronics to avoid some of the drawbacks in conventional pianos, such as the extreme weight and lack of mobility, and the propensity for string pianos to go out of tune fairly rapidly, there have been few electronic pianos that have been commercially successful. Commercial electronic pianos with which I am familiar have utilized tone generators of one sort or another controlled by the keyboard and feeding an amplifier. The amplifier oscillations are supplied to a loudspeaker, and all of the piano tones seem to be emanating from the one loudspeaker. This is contrary to the experience of pianists who are used to hearing the tones come from different parts of the piano. Specifically, and as will be obvious, in a conventional piano, the bass tones emanate from the left side, the treble tones from the right side, and intermediate tones from in between. Thus, it seems unnatural to a skilled pianist to have all of the tones emanate from a single position.

Thus, in accordance with the present invention, and forming one object thereof, it is proposed herein to provide a stereophonic electronic piano wherein the tones appear to emanate from approximately the correct positions relative to the keyboard.

More specifically, it is an object of the invention to provide an electronic piano having a pair of loudspeakers, one at either end of the keyboard, respectively being more efficient at the bass and treble ends of the audio spectrum of the piano, whereby the bass tones appear to emanate from the left end, the treble tones from the right end, and intermediate tones from in between.

A more specific object of the present invention is to provide a stereophonic electronic piano utilizing two similar loudspeakers at opposite ends of the keyboard, but which loudspeakers differ in inherent characteristics, and are mounted differently, whereby to produce bass notes relatively adjacent the left end of the keyboard and treble tones relatively adjacent the right end of the keyboard, with intermediate tones in between.

Other objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. I is a perspective view of an electronic piano constructed in accordance with the principles of the present invention;

FIG. 2 is a fragmentary sectional view taken through the upper portion of the piano above the keyboard substantially along the line 22 in FIG. I;

FIG. 3 is a fragmentary perspective view showing the mounting of one of the loudspeakers above the keyboard; and

FIG. 4 is an exploded-perspective view similar to FIG. 3 but showing the parts in spaced relationship.

Turning now in greater particularity to the drawings, and first to FIG. I, there will be seen an electronic piano identified generally by the number and including a case 12 having a keyboard 14 comprising the usual piano keys. A substantially vertical, but slightly inclined front panel 16 is provided above the keyboard, leading to the top 18 of the case. A music rack 20 extends above the top of the case.

The usual key bed 22 is provided beneath the keyboard 14, and a vertical panel 24 is disposed below the bed and recessed relative thereto. The panel 24 is covered, at least in part, with a grill cloth, and a loudspeaker 26 is mounted in the panel behind the grill cloth. Feet 28 extend forwardly from the piano case 12, specifically the front panel 24 thereof, for stability. A sustaining pedal 30 likewise is provided.

In addition to the loudspeaker 26, two loudspeakers are provided in the substantially vertical panel 16 and relatively at opposite ends of the keyboard. Specifically, there is a loudspeaker 32 provided substantially at the left or bass end of the keyboard, and there is a loudspeaker 34 provided adjacent the right or treble end of the keyboard. Loudspeakers 32 and 34 both are of the oval or elliptical type, having their long axes parallel to the length of the keyboard, whereby physically to spread the sound out somewhat along the keyboard without requiring undue height. The speakers are respectively positioned behind acoustically transparent panels 36 and 38, and these acoustically transparent panels 36 and 38 (see also FIG. 2) are of any well-known type, such as grill cloth, perforated sheet metal, etc.

Considering now FIG. 2 in greater detail, tone generators 40 are shown schematically. These tone generators may be of any desired or suitable type, there being one tone generator for each key of the keyboard 14. Alternatively, there could be a lesser number of tone generators which would be capable of being tuned to the note corresponding to a respective key. These can be electronic oscillators, or preferably they are vibratile reed generators in capacitive relation with a pickup, as in the commercially most successful electronic pianos sold to date, namely, those sold by The Wurlitzer Company. The tone generators are connected to the amplifier 42, and this amplifier is connected to the three loudspeakers. Although it is possible that the principles of the present invention could be carried on by electronic filtering to deliver only certain tones to the various speakers, in the preferred embodiment the speakers are all connected in parallel. One lead, as indicated at 44, extends to the voice coil of the speaker 32, while a second lead 46 from the amplifier is connected to the voice coil of the loudspeaker 34, while a third lead 48 is connected from the amplifier to the loudspeaker 26.

The loudspeaker 26 is of a full range type intended to reproduce the entire gamut of the instrument with relatively uniform efficiency, and provides little in the way of directivity. However, it does provide a good solid base for all of the tones.

The loudspeaker 32, as noted heretoforeand as seen specifically in FIGS. 3 and 4-, is of the oval or elliptical variety, and has a bracket 50 secured to the basket of the loudspeaker on the back thereof. The bracket 50 includes a top plate 52 and a bottom plate 54 in spaced parallel relation thereto, both of these plates being parallel to the speaker axis. Vertical end plates 56 interconnect and brace the top and bottom plates 52 and 54 respectively. The plates 52 and 54 are provided with aligned holes 58 in spaced relation.

Internally of the piano there is a vertical wall 60 disposed rearwardly of the keyboard. A horizontal wall or shelf 62 extends forwardly therefrom overlying the rear end of the keyboard. Brackets 64--are fixed to the wall or shelf 62 relatively adjacent the opposite ends of the keyboard, being fixed by spot welds or otherwise, and include forward portions 66 which incline upwardly at a shallow angle. Each of the inclined portions 66 is provided with a pair of elongated bolts 68 perpendicular to the respective inclined portion and having threaded upper ends. The bolts project through the holes 58 in the upper and lower plates of the speaker mounting brackets 50, and nuts 70 are threaded on the upper ends thereof to mount the speakers on the brackets 64, and hence on the shelf 62. The angle of inclination of the inclined bracket portions 66 is such as to dispose the forward faces of the speakers parallel to the nearly vertical front panel 16 of the piano case.

As will be understood. up to this point both speakers 32 and 34 are mounted identically. The speakers appear identical, but are not. The left speaker 32 is of a relatively soft cone design, and has a natural resonant frequency on the order of 99-100 cycles per second, while the right speaker 34 has a stiffer cone and has a naturally resonant frequency on the order of 128-140 cycles per second. Thus, inherently, the speaker 32 tends relatively to emphasize the bass tones, while the speaker 34 tends relatively to emphasize the higher tones. In addition to this, a gasket 72 is fixed to the front of the loudspeaker 32, and seals the loudspeaker to the panel 16. On the other hand, the speaker 34 is not provided with a gasket, and hence is spaced, as is indicated at 74, from the panel 16 by the thickness of the gasket 72.

Since the speaker 34 is spaced from the front panel 16 as indicated at 74, a significant amount of the back wave from the speaker 34 exits through the space 74, thus tending to cancel the front wave at relatively low frequencies. As will be understood, the presence or absence of the back wave at higher frequencies is relatively insignificant. Thus, the speaker 34 furthertends to discriminate against the lower frequencies, while maintaining relatively high efficiency with respect to the higher frequencies. Conversely, since the speaker 32 is sealed to the front panel 16, the back wave cannot exit adjacent the front wave, and hence does not tend to cancel the front wave. Thus, there is no significant diminution of the front wave, and the relatively low-frequency efficiency is maintained.

As will be understood from the foregoing, any tone generatedby one of the tone generators 40 is supplied to the three loudspeakers. Bass tones are relatively emphasized by the loudspeaker 32, while treble tones are relatively emphasized by the speaker 34. As will be understood, neither speaker completely discriminates against the tones toward which it is relatively inefficient, but reproduces them at a lower level. The speaker 26 reproduces all of the tones at substantially equal intensity. Thus, the bass tones appear to emanate mainly, but not entirely, from the left end of the keyboard, as is the case with a conventional piano wherein the string is located relatively adjacent the left end of the keyboard and roughly in alignment with the corresponding key, whereby the tone is primarily located at that position, but

not entirely, due to the resonance of the sound board which tends to spread out the sound to a considerable extent. Conversely, treble tones are primarily located adjacent the speaker 34, but not entirely so, just as in a conventional string piano. Intermediate tones appear to emanate from an intermediate location, whereby all of the tones appear to be spread out across the keyboard in much the same fashion as with a conventional piano. The speaker 26 is not essential, and portable electronic pianos are made without this speaker. However, it is a valuable adjunct, since it acts somewhat in the nature of a sounding board and tends to spread out and provide a mellowness to all of the tones.

The invention is claimed as follows:

1. An electronic piano including a case, a plurality of keys arranged in a keyboard and supported by said case, said case having upstanding panel means presented toward said keys, tone generator means in said case and controlled by said keys to provide electric oscillations corresponding to the musical tones related to the respective keys, amplifier means in said case electrically connected to said tone generator means for amplifying the electric oscillations therefrom, and loudspeaker means in said case electrically connected to the output of said amplifier means to convert the electric oscillations into audible sound, said loudspeaker, means including first and second speakers mounted in said case relatively adjacent the opposite ends of the keyboard, each speaker being connected to the same output of said amplifying means, the first speaker being disposed adjacent to the bass end of the keyboard for reproducing bass tones, and the second speaker being disposed adjacent to the treble end of the keyboard for reproducing treble tones, whereby the tones reproduced by said loudspeaker means appear to be distributed across said keyboard in accordance with tonal frequency, the natural frequency of the first speaker being lower than the natural frequency of the second speaker, the speakers being mounted at openings in said panel means that are presented toward said keys, said first speaker being peripherally sealed to said panel means to isolate substantially the forward and back waves emanating therefrom, and said second speaker being peripherally spaced from said panel means to permit local interference of the back wave and the front wave of the second speaker for partial cancellation of relatively bass tones.

2. An electronic piano according to claim 1 in which both speakers are substantially the same size.

3. An electronic piano according to claim 1 in which both speakers are oval speakers.

4. An electronic piano according to claim 1 In which the first speaker has a natural frequency of the order of 99-100 cycles per second and the second speaker has a natural frequency of the order of 128-140 cycles per second.

5. An electronic piano according to claim 1 in which said loudspeaker means further includes a third speaker underlying said keyboard and intermediate said first and second speakers for producing bass-to-treble frequencies at approximately equal intensity. 

1. An electronic piano including a case, a plurality of keys arranged in a keyboard and supported by said case, said case having upstanding panel means presented toward said keys, tone generator means in said case and controlled by said keys to provide electric oscillations corresponding to the musical tones related to the respective keys, amplifier means in said case electrically connected to said tone generator means for amplifying the electric oscillations therefrom, and loudspeaker means in said case electrically connected to the output of said amplifier means to convert the electric oscillations into audible sound, said loudspeaker means including first and second speakers mounted in said case relatively adjacent the opposite ends of the keyboard, each speaker being connected to the same output of said amplifying means, the first speaker being disposed adjacent to the bass end of the keyboard for reproducing bass tones, and the second speaker being disposed adjacent to the treble end of the keyboard for reproducing treble tones, whereby the tones reproduced by said loudspeaker means appear to be distributed across said keyboard in accordance with tonal frequency, the natural frequency of the first speaker being lower than the natural frequency of the second speaker, the speakers being mounted at openings in said panel means that are presented toward said keys, said first speaker being peripherally sealed to said panel means to isolate substantially the forward and back waves emanating therefrom, and said second speaker being peripherally spaced from said panel means to permit local interference of the back wave and the front wave of the second speaker for partial cancellation of relatively bass tones.
 2. An electronic piano according to claim 1 in which both speakers are substantially the same size.
 3. An electronic piano according to claim 1 in which both speakers are oval speakers.
 4. An electronic piano according to claim 1 in which the first speaker has a natural frequency of the order of 99-100 cycles per second and the second speaker has a natural frequency of the order of 128-140 cycles per second.
 5. An electronic piano according to claim 1 in which said loudspeaker means further includes a third speaker underlying said keyboard and intermediate said first and second speakers for producing bass-to-treble frequencies at approximately equal intensity. 